1. Field of Invention
The present invention relates to a driving circuit structure. More particularly, the present invention relates to a driving circuit structure for driving light-emitting loads.
2. Description of Related Art
Due to the development in light-emitting diode (LED) technology in recent times, the output luminance and the lighting efficiency of LEDs have improved dramatically. Therefore, LEDs are gradually replacing traditional lamps and are being used in modern lighting devices. For example, LEDs can be used in household lighting devices, vehicle lighting devices, flashlights, liquid crystal display (LCD) panel backlights, traffic signs, guideposts and other device.
The LED is a direct current (DC) load. In an application with multiple LEDs, the magnitude of the current going through each of the LEDs may be different because each LED may have slight differences in its characteristics, such that the output luminance may be uneven in the electronic devices (e.g., LCD panels) utilizing the LEDs, and also, the working durability of each LED may be shortened. Recently, LEDs made using cutting-edge techniques have a small impedance and a compact structure. In this case, when there is a variation in the driving voltage of the LED driving circuit, this may result in a significant variation in the operating current through the LED.
Many LED current balancing solutions have been developed in an effort to solve the problem of uneven currents on LEDs. A traditional power supply circuit with a current balancing feature may include linear voltage adjusters, low-pass filters and several current mirrors. However, the traditional power supply circuit with a current balancing feature utilizes a large number of linear voltage adjusters and current mirrors for corresponding to the LED loads, such that the power consumption of the circuit is high, the efficiency thereof is low, and the circuit requires many components and is therefore complex.